Magnetic circuit breaker



May 15, 1962 J. E. SCARPA MAGNETIC CIRCUIT BREAKERS 2 Sheets-Sheet 1 Filed Feb. 1, 1961 y 1962 J. E. SCARPA 3,035,138

MAGNETIC CIRCUIT BREAKERS Filed Feb. 1, 1961 2 Sheets-Sheet 2 40 Q P ,i ,7 -1 i .95 z 3a 94 I 12/2677 United Filed Feb. 1, 1961, Ser. No. 86,367 9 Claims. (Cl. 200106) The present invention relates generally to circuit breakers and relates more particularly to magnetically operated circuit breakers having high shock resistant characteristics. Specifically, the magnetically operable electric circuit breaker of the present invention is intended for use in situations and under conditions where there is a possibility or actual existence of high shock loadings applied directly to the circuit breaker or to structure supporting the circuit breaker.

It is required that electric circuit breakers be employed as safety devices in electric circuits and as a means for the protection of electrical devices controlled by such circuits. Such circuit breakers are required to operate when subjected to a 125% to 200% electrical overload beyond design and rated values thereof. Magnetically operated circuit breakers are commonly used for this purpose; however, prior circuit breakers have been unable to withstand shock loadings in excess of approximately 25 Gs without inadvertent and undesirable tripping thereof to interrupt a circuit controlled thereby. This level of shock loading is common and, even though experienced for only a relatively short time interval, has been sufficient to render prior magnetic circuit breakers impractical for many installational situations.

In instances where magnetic circuit breakers are subjected to forces and shock loadings induced by nearby high explosives or by other means, shock loadings in excess of 1000 Gs are common. Shocks of this type may be artificially induced as by, for example, mounting an object to be tested on a platform and thereafter striking the platform with a 400-pound hammer accelerated through an are having a radius of several feet. In practice, such loadings are actually produced in the firing of large guns, missile launchings and the like. In industrial applications, operation of drop hammers, certain types of presses and forging machines, as well as in mobile earth-moving equipment and the like, such high shock loadings are also experienced.

Prior magnetic circuit breakers have also included relatively complex arm, lever and latch mechanisms that have been relatively expensive, difficult to calibrate and align and relatively large in comparison to the rated characteristics thereof. In some instances, thermal types of circuit breakers have been employed and a portion of these have been known to withstand high shock loading. However, thermal types of circuit breakers are relatively large and heavy, as well as requiring an excessive time interval, while being subjected to an overload, before they are tripped. Also, thermal circuit breakers require a time interval before they may be reset. In many instances, a tripping time interval of from two to five milliseconds at a 125% to 200% overload is necessary to satisfy requirements for the protection of expensive equipment controlled by circuits in which such circuit breakers are used. In still further prior circuit breakers, it has been possible for uninformed or careless operators to maintain the circuit breaker in a closed condition through manipulation or holding of an external handle, button, knob or reset mechanism. To avoid possible damage of equipment protected by a circuit breaker, it is therefore necessary that the construction be such as to prevent any such adverse use thereof.

It is therefore one important object of the present invent-ion to provide a magnetically operable circuit breaker 3,035,138 Patented May 15, 10 52 having features of novelty enabling the circuit breaker to withstand high shock loadings from any direction without inadvertent tripping thereof.

It is another object of the present invention to provide a magnetic circuit breaker that is relatively small in size, light in weight, eflicient in operation and relatively inexpensive in manufacture.

A further object of the invention is to provide a magnetic circuit breaker including means for withstanding high shock loading and which may be actuated or tripped in a comparatively short time interval during an electrical overload condition.

Still another object of the invention is to provide a magnetically operable circuit breaker having a plurality of latch mechanisms so arranged and constructed to maintain electrical contacts in a closed position, even though the circuit breaker and the latch mechanisms therein are subjected to high shock loadings from various directions and in excess of 1000 times gravitational force.

A further important object of the invention is to provide a magnetic circuit breaker having features of novelty and mechanism to prevent maintenance of electrical contacts therein in a closed position when the circuit breaker is subjected to an electrical overload.

Other and further important objects of the invention will become apparent from the disclosures in the following detailed specification, appended claims and accompanying drawings, wherein:

FIGURE 1 is a perspective view of the exterior of the present magnetic circuit breaker;

FIG. 2 is an enlarged exploded isometric view showing the various component parts of the present circuit breaker and with the outer case removed;

FIG. 3 is a sectional view through the present circuit breaker as taken substantially as indicated by line 3--3, FIG. 1 and with the case removed, the circuit breaker being shown in an unlatched or tripped position;

FIG. 4 is an enlarged fragmentary sectional View showing portions of one of the latches and operating means therefore, the parts being shown in a normal position prior to setting the circuit breaker;

FIG. 5 is a fragmentary view similar to FIG. 4 showing the latch mechanism in a set or latched position;

FIG. 6 is a fragmentary sectional View also similar to FIG. 4 and showing the latch mechanism in a position during which the circuit breaker is being subjected to an electrical overload and at a moment just prior to tripping thereof; and

FIG. 7 is an enlarged fragmentary sectional view showing rotation limiting means for components of the circuit breaker and taken substantially as indicated by line 77, FIG. 3.

With reference to the drawings, the magnetic circuit breaker of the present invention is indicated in FIG. 1 generally at 10. The circuit breaker is housed in a suitable rectangular container 11 that may have an open top as at 12, the container serving to surround the mechanism of the circuit breaker and being secured to a frame 13 as by suitable screws 14. A pair of terminal studs 15 extend from the container 11 and serve as a means for attachment of the circuit breaker in a circuit to be protected thereby.

As shown primarily in FIGS. 2 and 3, the terminal studs 15 are insulated from and extend through the frame 13. The terminal studs 15 are further connected by means of leads 16 to contact members 17 that are carried by tubular supports 18 which are, in turn, secured to and depended from a lower portion of the frame 13. As shown, the frame 13 has integral X-shaped frame members 20 interconnecting an integral upper end portion 21 and a lower end portion 22. The members 20 are depended from common lateral edges of the end portions 21 and 22, thus to define a cavity for reception of the balance of the mechanism of the circuit breaker. An annular boss 23 is disposed from the inner area of the frame members 2t), there being a supporting shaft 24 positioned coaxial with the boss 23. The boss 23 is further provided with an annular recess 25, there being a notch 26 in a wall of the recess for reception of one end of an inner rotor torsional return spring 27. The spring 27 is adapted for disposition about the shaft 24 and within the recess 25.

An outer rotor, indicated generally at 349, is adapted for pivotal disposition in the cavity of the frame 13, the boss 23 being disposed within a central opening 31 in the outer rotor 34 The outer rotor 3G is circular and provided with a peripheral flange 32 disposed in one direction from the rotor. The flange 32 has an inner surface 33, there being a plurality of strike portions 34 having notches 35 and disposed outwardly from the flange 32. The strike portions 34 are shown as being four in number and arranged in an equally spaced angular relationship and laterally diametrically opposite each other about the flange 32. For a purpose to be hereinafter more fully described, the outer rotor 30 is further provided with an arcuate slot 36.

An inner rotor, indicated generally at is adapted for surface engagement with the outer rotor 30 and has a central bore 41 for reception of and pivotal disposition about the shaft 2 A slot 42 in the face of the inner rotor 40 is adapted for reception of one end of the spring 27. Accordingly, the inner rotor 40 is rotatably biased in the direction of the arrow 43, relative to the frame 13 and within the outer rotor 34) by means of the spring 27. The inner rotor 40 is further provided with a central boss 43 in which there is a central recess 44, there being a notch 45 in a wall of the recess 44. A torsion spring 46 is adapted for disposition in the recess 44, one end thereof being disposed in the notch 45.

One lateral surface of the inner rotor 40 has a plurality of magnetic pole pieces 47 disposed outwardly therefrom. The pole pieces 47 are generally L-shaped and each have a portion 48 that is spaced from and disposed generally parallel to the surface of the inner rotor 4t whereby to define an open area therebetween. Each of the portions 38 of the pole pieces 47 has a planar end surface 50 for a purpose to be hereinafter more fully described. The portions 48 of the pole pieces 47 are further provided with apertures 51 that are adapted rotatably to receive and support a shaft 52 that is depended from and connected to an inner latch member 53. The member 53 is generally circular and has a flat surface 54. A pin 55 is disposed laterally from an edge of the member 53 diametrically opposite the flat surface 54. The shaft 52 extends through the aperture 51 and into the area between the portion 43 of the pole pieces 47 and the surface of the inner rotor 40. The shaft 52 has an outer latch arm 56 connected thereto and depended radially outwardly therefrom. A torsion spring 57 is also disposed about the shaft 52 and between the arm 56 and the pole pieces 47, there being suitable notches in these elements for reception of ends of the torsion spring 57. The spring 57 serves rotatably to bias the outer latch arm and the inner latch member in the direction of the arrows 58. While only a single latch structure, including the inner latch member 53 and outer latch member 56, have been described, it is to be understood that, as shown, there are four of these structures and that the construction thereof is identical.

The inner rotor at} is further provided with a pair of L-shaped contactmembers at that are secured in angular spaced relationship to the surface of the inner rotor as by suitable screws 61, there being an insulating member 62 positioned between the contact members 64 and the surface of the inner rotor it). The contact members carry contacts 63 that are carried by portions of the contact members extending radially from the periphery of the inner rotor 4-0, the contacts 63 being faced in a common circumferential direction. The contacts 63 are adapted for cooperation with the contacts 17 carried by the frame 13. As also shown in FIG. 2, the in-- ner rotor 40 is provided with an arcuate slot 64 that is in tended for alignment with the slot 36 in the outer rotor 49. The slots 36 and 64 are adapted for reception of a. limit pin 65 that is carried by and disposed from one. of the frame members 20 of the frame 13, this particus lar associationb'eing shown in deail in FIG. 7.

As shown in FIGS. 2 and 3, a formed coil 70 having at central opening '71 is disposed about the boss 43 of the inner rotor 46 the outer periphery of the coil 70 being;

disposed within" the confines of the pole pieces 47 and having a thickness substantially equal to the height of the pole pieces 4-7 from the inner rotor 40. The coil 70.- is shown as being wound from insulated wire; however,v the coil may also be wound from anodized aluminum; foil, or the like.- The pins 55, depended from the inner latch members 53, extend over a lateral surface of the: coil 70. The coil 70 has opposite ends of the leads there-- from, as indicated at 72 and 73, which are connected, as shown, to the contact members 66. The windings of? the coil 70 are therefore in series with the contacts 6 3 and-the terminal studs 15. g

As further shown in FIGS. 2 and 3, an X-shaped armature 89 is positioned in contact with an outer end surface of the boss 43 and has integral arm portions 81: which extend radially from a central area of the armature: Sit. The central area of the armature is further pro-- vided with an aperture 82 for reception of one end of the torsion spring 46, thus lightly biasing the armature. 80 in a direction indicated by the arrow 83. The arma-- ture iitl is further provided with pole pieces engaging: members 84 that are depended integrally from outer ends of the arm portions 81 and disposed substantially normal to the arm portions 81. The members 84 have V inner edges 85 that are positioned adjacent the outer pe-- riphery of the coil 70, the members 84 being adapted? for cooperation with the faces 5% of the pole pieces 47.. The arm portions 81 further have radially disposed edges 86 that are adapted for cooperation with the pins 555 depended from the inner latch members 53.

The armature 80 is provided with a needle bearing: member 37 disposed from the central area thereof, the: member 87 being adapted for disposition in and cooperation with a conical recess 38 formed in a central area of. a latch receiver 9t and a boss 91 disposed therefromw Thus, the armature 84} is maintained in axial alignment. with the other structures of the present circuit breaker... The latch receiver 94) is generally circular and has ra-- dially extending lugs 92 each with openings 93 therethrough. The lugs @2 are adapted to overlie fillet por-' tions 94 formed integrally in the frame 13, the latch receiver being secured to the fillet portions 94 by means of suitable screws 95 which threadably engage bores 96- in each of the fillet portions 94-. The latch receiver 90: has a peripheral flange 97 which extends toward the frame 13 and has inner and outer diameters substantially equal to the respective inner and outer diameters of the flange 32 of the outer rotor 3 An inner surface of' the flange 97 is provided with a plurality of semicircular recesses 98 that are, as will be hereinafter more fully described, adapted for cooperation with the inner latch. members 53.

With reference to FIGS. 1, 2 and 3, the present circuit breaker is provided with an external toggle lever 100- which extends through a boss 161 and into the cavity defined within the frame 13. The toggle lever 1th} is pivoted on a pin M32 disposed laterally through the boss Lttltl. The inner end of the toggle lever 100 is generally L-shaped whereby to dispose an arm portion 103 thereof adjacent a side of the outer rotor 3h remote from the strike portions 34. A free end of the arm 103 is bifurcated as at The and adapted for cooperation with a pin 105 depended from the outer rotor 30. Accordingly, as the toggle lever 100 is moved in the directions of the arrow 106, the outer rotor 30 will also be moved in the directions of the arrow 107.

Operation of the present circuit breaker is illustrated primarily in FIGS. 4, 5 and 6 and in conjunction with FIGS. 2 and 3. In FIG. 4, the mechanism of the circuit breaker is shown as being in condition to be cocked or set. It is to be noted that the flat surface 54 of the inner latch member 53 is substantially parallel to the inner surface 33 of the flange 32 of the outer rotor 30 and that the outer latch arm 56 is slightly engaged in the outer end of the notch 35 in the strike portion 34, also carried by the outer rotor 30. Upon operation of the toggle lever 10%), the outer rotor will be rotated in the direction of the arrow 110, FIG. 4, whereby to move the inner rotor 46, storing torsional force in the spring 27. As shown, the inner latch member 53 is biased in the direction of the arrow 58 by the torsion spring 57 and, when the inner rotor 40 reaches the position shown in FIG. 5, the inner latch member 53 will rotate as shoWn into the recess 98. Also, the outer latch arm 56 will move to the base of the notch in the strike portion 34. When the components are in the position shown in FIG. 5, the contacts 63 will be in engagement with the contact 17, whereby to complete a circuit from one of the terminal studs 15, through one lead 16, one set of contacts 17-63, through the coil '70, the other set of contacts l763, the other lead 16 and the other terminal stud 15. Thus the circuit is complete through the circuit breaker.

When an electrical overload condition is experienced, an increased fiux density will be manifest in the coil 7% and magnetically cause the armature 80 to be rotated to the position shown by the solid lines in FIG. 6 and the pole piece engaging portions $4 to engage the face So of the pole piece 47. Also, at this time, torsional force is stored in the torsion spring 46 and the edge 86 of the armature arm portions 81 will engage the pin 55 thereby to rotate the inner latch member 53, shaft 52, and outer latch arm 56 in a direction to remove the outer latch arm 56 from the notch 35 in the strike 34 and further to rotate the inner latch member 53 out of engagement with the recess 98. With the latching action against rotation of the inner rotor 4% being removed, the force stored in the torsion spring 27 will rotate the inner rotor in the direction of the arrow 111, FIG. 6, to dispose the components in the positions shown by the dotted lines in FIG. 6. At this time, the contacts 63 will be separated from the contacts 17 whereby to open the circuit across the terminal studs 15.

As long as an electrical overload condition exists, the toggle lever 1% may be moved in the directions of the arrow 1%, to rotate the outer rotor 38. However, the latch components will remain in the position shown by the solid lines in FIG. 6, thus to prevent resetting of the circuit breaker under such conditions.

While the operation of the present circuit breaker has been described in association with a single set of latching components, it is to be understood that all of the individual latches disposed about the periphery of-the inner rotor 40 operate identically and simultaneously. Location of the four latches is such that while high shock loadings in any one direction may have the effect of unlatching one or two of the latches, the balance of the latches serve to maintain the circuit breaker in a cocked or set position with the loading forces acting to increase the holding force of these latches. Further, the use of the rotary sliding construction between the inner latch members 53 and the notches 98 of the flange 97 of the latch receiver ht), high holding force against rotation of the latches out of the notches is maintained while very little force is required on the pins 55, as exerted by the armature S0, to rotate the inner latch members 53 out of engagement with the notches 98. As described hereinbefore, the arcuate slots 36 and 64 in the outer rotor 3t and inner rotor 4i respectfully cooperate with the limit pin 65 carried by the frame 13 to limit angular movement of the inner and outer rotors about the supporting shaft 24.

Having thus described the invention and the present embodiment thereof, it is desired to emphasize the fact that many modifications may be resorted to in a manner limited only by a just interpretation of the following claims.

I claim:

1. A magnetic circuit breaker comprising: a frame structure; electrical terminals carried by and insulated from said frame structure; first electrical contacts connected to said terminals; a latch receiver carried by said frame structure in spaced relationship thereto; an outer rotor; an inner rotor, said outer and inner rotors being disposed intermediate said frame structure and said latch receiver; strike means carried by said outer rotor; latch means carried by said inner rotor and cooperable with said strike means; latch receiving means in said latch receiver, said latch means also being cooperable therewith; second electrical contacts carried by said inner rotor and adapted for engagement with said first contacts; means disposed between said frame structure and said inner rotor for biasing said second contacts in a direction away from said first contacts; a coil disposed adjacent said inner rotor, said coil being connected in series with said terminals through said first and second contacts; magnetic pole pieces carried by said inner rotor and disposed about said coil; a rotatable armature positioned adjacent said latch receiver and cooperable with said pole pieces to move said armature in response to an increased flux density in said coil beyond a rated value thereof, a portion of said armature being cooperable with said latch means upon said movement thereof; and means for moving said outer rotor whereby to rotate said inner rotor through said strike and latch means, engage said latch means with said latch receiving means and engage said first and second contacts, said increased flux density serving to move said armature, disengage said latch means from said latch receiving means and said strike means, thereafter to permit separation of said contacts by action of said biasing means.

2. A magnetic circuit breaker comprising: a frame structure; electrical terminals carried by and insulated from said frame structure; first electrical contacts connected to said terminals; a latch receiver carried by said frame structure in spaced relationship thereto; an outer rotor; an inner rotor, said outer and inner rotors being disposed intermediate said frame structure and said latch receiver; strike means carried by said outer rotor; latch means carried by said inner rotor and cooperable with said strike means; latch receiving means in said latch receiver, said latch means also being cooperable therewith, said strike, latch and latch receiving means being arranged in diametrically opposed pairs; second electrical contacts carried by said inner rotor and adapted for engagement with said first contacts; means disposed between said frame structure and said inner rotor for biasing said second contacts in adirection away from said first contacts; a coil disposed adjacent said inner rotor, said coil being connected in series with said terminals through said first and second contacts; magnetic pole pieces carried by said inner rotor and disposed about said coil; a rotatable armature positioned adjacent said latch receiver and cooperable with said pole pieces to move said armature in response to an increased flux density in said coil beyond a rated value thereof, a portion of said armature being cooperable with said latch means upon said movement thereof; and means for moving said outer rotor whereby to rotate said inner rotor through said strike and latch means, engage said latch means with said latch receiving means and engage said first and second contacts, said increased flux density serving to move said armature, disengage said latch means from said latch receiving means and said strike means, thereafter to permit separation of said contacts by action of said biasing means.

3. A magnetic circuit breaker comprising, in combination: a frame structure; electrical terminals carried by and insulated from said frame structure; stationary electrical contacts connected to said terminals; a latch receiver carried by said frame structure in spaced rela tionship thereto; an outer rotor; an inner, rotor, said outer and inner rotors being rotatably disposed intermediate said frame structure and said latch receiver; plural strike means carried by said outer rotor; plural latch means carried by said inner rotor and cooperable with said strike means; latch receiving means in said latch receiver, said latch means also being cooperable therewith, said strike, latch and latch receiving means 'being arranged in lateral diametrically opposed pairs; movable electrical contacts carried by said inner rotor and adapted for engagement with said stationary contacts; means disposed between said frame structure and said inner rotor for biasing said movable contacts in a direction away from said stationary contacts; a coil disposed adjacent said inner rotor, said coil being connected in series with said terminals through said movable and stationary contacts; magnetic pole pieces carried by said inner rotor and disposed about said coil; a rotatable armature positioned adjacent said latch receiver and cooperable with said pole pieces to move said armature in response to an increased flux density in said coil beyond a rated value thereof, a portion of said armature being cooperable with said latch means upon said movement thereof; manually operable means for pivotally moving said outer rotor whereby to rotate said inner rotor through said strike and latch means, engage said latch means With said latch receiving means and engage said movable and stationary contacts, said increased flux density serving to move said armature, disengage said latch means from said latch receiving means and said strike means, thereafter to permit separation of said contacts by action of said biasing means; and means for limiting angular rotation of said rotors.

4. A magnetic circuit breaker comprising, in combination: a frame structure; electrical terminals carried by and insulated from said frame structure; stationary electrical contacts connected to said terminals; a latch receiver carried by said frame structure in spaced relationship thereto; an outer rotor; an inner rotor, said outer and inner rotors being rotatably disposed intermediate said frame structure and said latch receiver; plural strike means carried by said outer rotor; plural latch means carried by said inner rotor and cooperable with said strike means, said latch means having a circular latch member; semicircular latch receiving means in said latch receiver, said latch means also being cooperable therewith; movable contacts carried by said inner rotor and adapted for engagement with said stationary contacts; means disposed between said frame structure and said inner rotor for biasing said movable contacts in a direc tion away from said stationary contacts; a coil disposed adjacent said inner rotor, said coil being connected in series with said terminals through said movable and stationary contacts; magnetic pole pieces carried by said inner rotor and disposed about said coil; a rotatable armature positioned adjacent said latch receiver and cooperable with said pole pieces to move said armature in response to an increased flux density in said coil beyond a rated value thereof, a portion of said armature being operable to rotate said latch means and said circular latch member upon said movement thereof; and manually operable means for pivotally moving said outer rotor whereby to rotate said inner rotor through said strike and latch means, engage said latch means with said latch receiving means and engage said movable and stationary contacts, said increased flux density serving to move said armature, disengage said latch means from said latch receiving means and said strike means, thereafter to permit separation of said contacts by action of said biasing means.

5. A magnetic circuit breaker comprising, in combination: a frame structure; electrical terminals carried by and insulated from said frame structure; stationary electrical contacts connected to said terminals; a latch receiver carried by said frame structure in spaced relationship thereto; an outer rotor; an inner rotor, said outer and inner rotors being rotatably disposed intermediate said frame structure and said latch receiver; plural strike means carried by said outer rotor; plural latch means carried by said inner rotor and cooperable with said strike means, said latch means having a circular latch member; semicircular latch receiving recesses in said latch receiver, said latch means also being cooperable therewith, said strike and latch means and said latch receiving recesses being arranged in lateral diametrically opposed pairs; movable contacts carried by said inner rotor and adapted for engagement with said stationary contacts; spring means disposed between said frame structure and saidv 'inner rotor for biasing said movable contacts in a direc-- tion away from said stationary contacts; a coil disposed adjacent said inner rotor, said coil being connected in series with said terminals through said movable and stationary contacts; magnetic pole pieces carried by said inner rotor and disposed about said coil; a rotatable. armature positioned adjacent said latch receiver and co-- operable with said pole pieces to move said armature in response to an increased flux density in said coil beyond a rated value thereof, a portion of said armature being operable to engage and rotate said latch means and said cir cular latch member upon said movement thereof; manually operable means for pivotally moving said outer rotor whereby to rotate said inner rotor through said strike and latch means, engage said latch means with said semicircular latch receiving recesses and engage said movable and stationary contacts, said increased flux density serving to move said armature, disengage said latch means from said latch receiving recesses and said strike means, thereafter to permit separation of said contacts by action of said biasing means; and means for limiting angular rotation of said rotors.

6. In a magnetic circuit breaker having electrical terminals, contacts movable into and out of engagement, a movable rotor for supporting movable elements of said contacts, a coil, a frame and means biasing said contacts toward an open position, the combination with said circuit breaker of a latch arrangement between said frame and said rotor, said latch arrangement comprising: a plurality of latches carried by said rotor, said latches being disposed in lateral opposed relationship; latch receiving recesses in a portion of said frame, portions of said latches being pivotally engageable with said recesses; and means operable upon an increased flux density in said coil to rotate said latch portions out of engagement with said recesses, said biasing means thereafter serving to move said rotor to separate said contacts.

7. In a magnetic circuit breaker having electrical terminals, contacts movable into and out of engagement, a movable rotor for supporting movable elements of said contacts, a coil, a frame and means biasing said contacts toward an open position, the combination with said circuit breaker of a latch arrangement between said frame and said rotor, said latch arrangement comprising: a plurality of latches carried by said rotor, said latches being disposed in lateral opposed relationships; latch receiving recesses in a portion of said frame, portions of said latches being pivotally engageable with said recesses; means operable upon an increased flux density in said coil to rotate said latch portions out of engagement with said recesses, said biasing means thereafter serving to move said rotor to separate said contacts; and means externally of said frame and operable through said latches to reengage said contacts only when said flux density is reduced below a predetermined level.

8; In a magnetic circuit breaker having electrical terminals, contacts movable into and out of engagement, a movable rotor for supporting movable elements of said 9 contacts, a coil, 21 frame and means biasing said contacts toward an open position, the combination with said circuit breaker of a latch arrangement between said frame and said rotor, said latch arrangement comprising: a plurality of latches carried by said rotor, said latches having 5 semicircular portions and being disposed in lateral opposed relationship; semicircular latch receiving recesses in a portion of said frame, said semicircular portions of said latches being pivotally engageable with said recesses; and armature means operable upon an increased flux density in said coil to engage and to rotate said latch portions out of engagement with said recesses, said biasing means thereafter serving to move said rotor to separate said contacts.

9. In a magnetic circuit breaker having electrical terminals, contacts movable into and out of engagement, a movable rotor for supporting movable elements of said contacts, a coil, a frame and means biasing said contacts toward an open position, the combination with said circuit breaker of a latch arrangement between said frame and said rotor, said latch arrangement comprising: a plurality of latches carried by said rotor and disposed peripherally about said coil, said latches having semicircular portions and being disposed in lateral opposed relationship; semicircular latch receiving recesses in a portion of said frame peripherally disposed about said latches, said semicircular portions of said latches being pivotally engageable with said recesses; armature means operable upon an increased flux density in said coil to engage and to rotate said latch portions out of engagement with said recesses, said biasing means thereafter serving to move said rotor to separate said contacts; and means externally of said frame and operable through said latches to re- 7 engage said contacts only when said flux density is reduced below a predetermined level.

References Cited in the file of this patent UNITED STATES PATENTS 1,576,276 Hedges et al Mar. 9, 1926 2,603,729 Ball July 15, 1952 2,705,272 Dobes et al Mar. 29, 1955 

